The present invention relates to video signal processing apparatus and, more particularly to a video signal processing apparatus in which insertion or extraction of image data at the field or frame unit is switched by detecting a motion amount of an image based on an energy ratio between a DC video signal component and an AC video signal component.
When a VCR (video cassette recorder) is used in a so-called program play in which a video signal recorded on a magnetic tape is reproduced under the condition that an overall reproducing speed is changed by changing a tape running speed in a range of from ten and several percents for pluses and minuses relative to a tape running speed of a normal reproduction mode, there has hitherto been proposed a video signal processing technique in which the magnetic tape on which the video signal is recorded is reproduced by a playback head and image is inserted into or extracted from a reproduced video signal. According to this video signal processing technique, image is inserted into or extracted from the reproduced video signal by a so-called frame synchronizer used in some suitable cases, such as when a PAL video signal is converted to an NTSC video signal.
In the video signal processing apparatus using such video signal processing technique, the frame synchronizer is composed of a memory and a memory controller and image is inserted into and extracted from image data by varying write data and read data of the memory. In this case, image is inserted into and extracted from image data only at the field unit. The reason that image is inserted into and extracted from image data only at the field unit is that, if image is inserted into and extracted from image data at the frame unit, when an image is a moving picture, image data is coarsely inserted into and extracted from image data at the frame unit and a motion on the image becomes rough. Thus, a motion of image becomes unnatural when visually confirmed by the viewer. Therefore, each time image is inserted into and extracted from image data, odd field and even field are not kept continuous.
If odd fields are continued or even fields are continued with the result that odd field and even field are not kept continuous as described above, there then occurs the flicker that a picture is shifted in the upper and lower direction.
To remove the flicker in which the picture is shifted in the upper and lower direction, there has been so far used a technique called "Y/C Add" using a correlation of a television signal in the time axis direction. When however such technique is used, it is frequently observed that a resolution of a reproduced picture is deteriorated considerably. The resolution of the reproduced picture is considerably deteriorated in the lines extending in the oblique direction on the picture.
As described above, since image is inserted into and extracted from image data at the field unit in the video signal processing apparatus, each time image is inserted into and extracted from image data, odd field and even field cannot be kept continuous and hence a quality of a reproduced picture is deteriorated considerably.